This invention relates to a process for making multicolored soap bars and particularly to a process enabling the production of an improved variegated, striated or marbleized soap bar wherein the color striations are sharper and more distinct relative to soap bars produced by prior art processes.
Various processes are know wherein milled soap of a base color such as white is introduced into a more or less conventional double barrel plodder along with a suitable coloring agent whereby the extruded column exhibits color striations, and the column is subdivided and pressed to form bars of variegated soap. For example, see Compa et al U.S. Pat. No. 3,485,905 which teaches adding the coloring agent in the form of an aqueous dye solution to the vacuum chamber between the upper and lower plodder barrels. Other apparatus and processes for producing marbleized or striated soap are disclosed, for example, in Matthaei U.S. Pat. Nos. 3,832,431; 3,769,225 and 3,673,294; Meyer et al U.S. Pat. No. 3,663,671 and Patterson U.S. Pat. No. 3,676,538 among others.
The coloring agent employed is usually a color dye or pigment material that is not harmful to the skin and usually dissolved and/or dispersed in water and suitably introduced into the base soap being worked in the plodder. Preferably the coloring agent is a water soluble dye certified by the Food and Drug Administration for external cosmetic or drug use, i.e., FD&C or D&C or external D&C dyes. A water soluble coloring agent is preferable to a water insoluble dye or pigment material because the former avoids any problem of an insoluble color residue when the soap bar is being consumed and tend to be more suitable for use on the skin.
A disadvantage has been noted, however, in multicolored soap bars incorporating water soluble coloring agent in that the stripes or streaks may not be distinct or show sharp contrast with the base soap color at their edges, and this is particularly apparent at the surface of the bar. Apparently, due to the moisture content of the base soap, the colors leach into adjoining areas which results in interface bleeding between the background and colored portions and a "washed out" appearance. This bleeding effect also occurs when water insoluble pigments are used as the coloring agent, although to a lesser degree. The bleeding effect becomes increasingly more apparent as the moisture content of the soap increases, particularly over 12% moisture by weight.
The invention includes the advantageous discovery that when a coloring agent is dispersed in a liquid oil vehicle as described herein before being combined with the base soap material, the foregoing bleeding effect is minimized and the streaks or stripes in the resulting bars are sharper and more distinct, thereby creating greatly improved appearance. Moreover when the coloring agent is dispersed in an oil vehicle according to the invention the total viscosity of the dispersion is increased so that less coloring agent is required to obtain the same effect and the color variegation is more distinct.
A primary advantage of the invention is to provide a colored material comprising a dye or pigment dispersed, suspended, dissolved, or emulsified in an oil vehicle that when combined with a base soap material results in an attractive soap bar that exhibits a minimum of interface bleeding.
A further advantage of the invention is to permit the use of high moisture content base soap material, i.e., 12% or more water by weight, while maintaining the color distinctiveness required for a saleable product.
Still further, the use of oil vehicles for the coloring agent provides the bar with an improved "feel" and soothing and emollient effects to the skin.
A still further advantage of the invention is the reduction of excess free alkali in the base soap material by using an oil vehicle containing fatty acids that neutralize excess free alkali.
A still further advantage of the invention is the use of less coloring agent to obtain a desired colored effect.
Still further, the invention can reduce the loss of perfume normally used in a soap bar through evaporation by using a perfume oil as the vehicle for the coloring agent.